1. Field of the Invention
The present invention relates to a solid electrolytic capacitor; and, more particularly, to a solid electrolytic capacitor capable of improving capacitance by maximizing volumetric efficiency of a capacitor element while pursuing manufacture of a miniaturized capacitor by injecting molding material on the anode terminal positioned at one side of a bottom surface of a molding unit to insulate the capacitor element from an anode terminal.
2. Description of the Related Art
Generally, a solid electrolytic capacitor is one of electronic parts used to interrupt DC and pass AC as well as to store electricity. As a representative solid electrolytic capacitor, a tantalum capacitor has been manufactured.
The tantalum capacitor is used for an application circuit low in a usage range of a rated voltage as well as for a general industrial device and particularly, it is frequently used to reduce noise of a circuit or a portable communication device with a poor frequency characteristic.
Such a capacitor is fundamentally manufactured by inserting a lead wire into a central portion of a tantalum element or a position except for the central portion or bending the inserted lead wire outside the tantalum element.
Further, as a method for assembling a lead frame to the tantalum element, there is used a method in which an anode terminal is drawn out through spot welding of an anode (+) lead wire and an anode (+) lead frame and an electrode terminal is drawn out through anode and cathode lead forming after mold-packaging.
FIGS. 1 and 2 are views showing a conventional solid electrolytic capacitor, wherein FIG. 1 is a perspective view showing the conventional solid electrolytic capacitor and FIG. 2 is a cross-sectional view showing the conventional solid electrolytic capacitor.
As shown in the drawings, the conventional solid electrolytic capacitor 10 includes a capacitor element 11 made of dielectric powder to determine capacity and characteristic of the capacitor, anode and cathode lead frames 13 and 14 connected to the capacitor element 11 to be easily mounted to a PCB (Printed Circuit Board), and an epoxy case 15 molded with epoxy to protect the capacitor element 11 against an external environment and form a shape of the capacitor element 11.
At this time, the capacitor element 11 includes a rod-shaped anode wire 12 which protrudes at one side at a predetermined length.
And, the anode wire 12 includes a pressure surface 12a with a flat external surface in order to increase a contact ratio with the anode lead frame 13 and prevent right and left shaking in welding.
Herein, a method for manufacturing the capacitor element 11 includes the steps of: sintering dielectric powder after forming it in a rectangular parallelepiped shape in a press process, forming a dielectric oxide film on the external surface through a formation process, and impregnating it into an aqueous solution of manganese nitrate in order to form a manganese dioxide layer made of solid electrolyte on an external surface through pyrolysis.
A process for connecting the anode and cathode lead frames 13 and 14 to the thus-manufactured capacitor element 11 includes the steps of: drawing out the anode terminal by welding the plate-shaped anode lead frame 13 on the pressure surface 12a of the rod-shaped anode wire 12 protruding at the one side of the capacitor element 11 at the predetermined length and drawing out the cathode terminal through the medium of a conductive adhesive coated on an external surface of the capacitor element 11 or the cathode lead frame 14.
And, the manufacture of the capacitor is completed through a final marking process after forming the epoxy case 15 by molding the capacitor element 11 electrically connected to the anode and cathode lead frames 13 and 14 with the epoxy in a cladding process.
The thus-manufactured conventional solid electrolytic capacitor 10 has problems in that capacitance is reduced and impedance is increasing as efficiency of volume occupied by the capacitor element 11 of the entire volume including the epoxy case 15 is dramatically deteriorated.